1. Field of the Invention
The present invention relates to a stop and start control apparatus of an internal combustion engine, and relates to an discharge prevention technique of an unburned fuel, which prevents fuel supplied to a specific cylinder from being discharged in an unburned state at the time of stopping the internal combustion engine.
2. Description of the Related Art
Recently, there is known an engine stop and start control apparatus for automatically stopping an internal combustion engine (hereinafter, also referred to as xe2x80x9cenginexe2x80x9d) when the vehicle stops and for automatically restarting the engine to start the vehicle when an instruction to start is given in the stopped state, in order to reduce a fuel consumption amount and exhaust gas during idling, from the viewpoint of environmental conservation, resources and energy saving or the like. This control is also called xe2x80x9cidling stopxe2x80x9d or the like.
It is known that, when the idling stop is automatically carried out, it is effective to control the stop position of the engine in order to minimize required energy at the time of starting the engine. Minimizing the required energy at the time of starting the engine brings about the advantages that an engine starting device used after idling stop such as a motor generator (MG) can be miniaturized, and the useful life of a battery can be elongated by reducing the electric energy.
As a method for quickly starting the engine, there is known an engine starting apparatus in which fuel is supplied into a combustion chamber of a cylinder at an expansion stroke at the time the engine is stopped, and then the fuel is combusted at the time the engine is started. By utilizing combustion pressure generated at this time, the cranking torque at the time of starting the engine is generated. For example, see Japanese Patent Application Laid-Open under No. 2002-4985.
However, even if the fuel is supplied to the combustion chamber of the cylinder at the expansion stroke at the time the engine is stopped, if a driver turns off an ignition switch thereafter, the driver should activate a starter by turning on the ignition switch at the time of the next engine start, and the engine is started by the torque of the starter generated at that time.
In this situation, since the crankshaft is rotated by the cranking operation of the starter, the fuel supplied in the combustion chamber of the cylinder is discharged through an exhaust port without being burned, which causes the problem of deterioration of emission.
The present invention is made in view of the above-described problem, and its object is to provide a stop and start control apparatus of an internal combustion engine, which prevents fuel supplied into a specific cylinder at the time of stopping the engine from being discharged in an unburned state.
According to one aspect of the present invention, there is provided a stop and start control apparatus of an internal combustion engine including: a stop control unit for performing a stop control by supplying fuel into a combustion chamber of a cylinder which is in a compression stroke and/or in an expansion stroke at a time of stopping the engine; an unburned fuel discharge preventing unit for preventing discharge of the fuel when it is estimated that the fuel in the combustion chamber of the cylinder is discharged in an unburned state, at a time of a stop control of the engine; a combusting unit for combusting the fuel supplied to the combustion chamber of the cylinder at a time of starting the engine; and a starting unit for starting the engine by utilizing combustion pressure obtained from the combusting unit and/or a motor.
The above-described stop and start control apparatus can be preferably used, for example, in an idling stop control and the like. In the stop control of the engine, fuel is supplied to the combustion chamber of the cylinder which is in the compression stroke and/or in the expansion stroke at the time of stopping the engine. The fuel is supplied, in advance, to generate a driving force at the time of starting the engine next time. At the time of starting the engine, the engine is started with the combustion pressure obtained by combusting the fuel supplied into the combustion chambers and/or the driving force by the motor. However, when the fuel which is thus supplied to the cylinder in advance is discharged without being combusted, deterioration of emission is likely to occur. Therefore, such a discharge of the fuel should be prevented. One example of the case where the fuel supplied in advance to the cylinder is discharged without being combusted is that the ignition switch is turned off when the engine stops with the fuel being supplied to the cylinder in the compression stroke and/or in the expansion stroke. Another example thereof is that the stop control fails and the engine cannot stop at the scheduled engine stop position.
In a preferred example, it is estimated that the fuel is discharged in the unburned state when an ignition switch is turned off during the stop control of the engine. When the ignition switch is turned off, the next engine start is performed by the cranking using the motor. When the engine is started in this case, the crankshaft is turned by the motor, and therefore there is the possibility that the fuel, which is sealed in the combustion chamber of the cylinder which is in the compression stroke and/or in the expansion stroke at the time of stopping the engine, is discharged through the exhaust port without being burned. Accordingly, the case in which it is estimated that the fuel is discharged in the unburned state can be made the case in which the ignition switch is turned off during the stop control of the engine.
The stop control unit may further include: a unit for supplying fuel, during operation of the engine, into the combustion chamber of the cylinder which is in the compression stroke and/or in the expansion stoke; and a unit for adjusting a crank angle position so that the engine stops at the cylinder which is in the compression stroke and/or in the expansion stroke, at the time of stopping the engine. In this case, in stopping operation of the engine, the cylinder of which combustion chamber is fed with fuel stops in the compression stroke and/or in the expansion stroke. This allows the generation of driving force to start the engine next time by igniting and burning the fuel in the cylinder.
The unburned fuel discharge preventing unit may prevent the fuel supplied to the combustion chamber of the cylinder which is in the compression stroke or in the expansion stroke, when it is estimated that the cylinder which is in the compression stroke or in the expansion stroke at the time of stopping the engine passes an exhaust stroke. The stop control of the engine is to supply the fuel to the cylinder which is in the compression stroke or in the expansion stroke at the time of engine stop, and to combust the fuel to generate the driving force at the time of starting the engine next time. However, when the stop control fails and the cylinder in which the fuel is supplied at the time of stopping the engine passes the exhaust stroke, the unburned fuel is discharged. Therefore, the stop control prevents this.
The engine may further include an opening and closing unit for opening and closing an exhaust valve, and when it is estimated that the cylinder, which is in the compression stroke or the expansion stroke at the time of stopping the engine, passes the exhaust stroke, the opening and closing unit prevents the fuel supplied to the combustion chamber of the cylinder which is in the compression stroke or in the expansion stroke from being discharged. According to this feature, when it is estimated that the cylinder to which the fuel is supplied reaches the exhaust stroke in the stop control, the unburned fuel is prevented from being discharged by closing the exhaust valve.
The unburned fuel discharge preventing unit may prevent discharge of the fuel by combusting the fuel by the combusting unit before the fuel supplied to the combustion chamber of the cylinder which is in the compression stroke or in the expansion stroke is discharged, when it is estimated that the cylinder which is in the compression stroke or the expansion stroke at the time of stopping the engine passes the exhaust stroke. According to this feature, when it is estimated that the cylinder to which the fuel is supplied in the stop control reaches the exhaust stroke, the unburned fuel is prevented from being discharged by compulsorily combusting the unburned fuel.
In a preferred embodiment, the starting unit may start the engine by utilizing combustion pressure obtained from the combusting unit when a first starting condition is established, and the unburned fuel discharge preventing unit may prevent discharge of the fuel by combusting the fuel by the combusting unit before the fuel inside the combustion chamber of the cylinder is discharged in the unburned state.
In another preferred embodiment, the starting unit may start the engine by utilizing combustion pressure obtained from the combusting unit and the motor, and starting supply of the fuel to the engine in a predetermined period, when a second starting condition is established. The unburned fuel discharge preventing unit may prevent discharge of the fuel by combusting the fuel by the combusting means, before the fuel in the combustion chamber of the cylinder is discharged in an unburned state.
The stop and start control apparatus of the internal combustion engine may further include a torque absorbing unit for absorbing an engine torque which is generated when the fuel in the combustion chamber of the cylinder is combusted by the combusting unit. Thus, the torque generated when the unburned fuel is burned by the combustion unit can be absorbed to suppress vibration and the like of the vehicle.
The torque absorbing unit may apply torque by the motor in a counter rotation direction to a rotation direction of the engine rotated by receiving the torque generated by the combustion of the fuel. According to this feature, the torque absorbing unit can be made, for example, a motor. By giving the driving torque of such a motor in the counter rotation direction to the rotation direction of the engine, the vibration generated due to the combustion of the unburned fuel can be canceled off and eliminated.
In a preferred specific example, the engine may further include a unit for displaying an alarm at a time of execution of an operation by the unburned fuel discharge preventing unit. The alarm display according to this example is to notify the driver that special processing to combust the unburned fuel is being performed, after turning off the ignition switch, and it is displayed on an operation panel or the like so that the driver can recognizes it at a glance. Consequently, by displaying such an alarm when the unburned fuel discharge preventing unit is in operation, even if the engine temporarily starts after the ignition switch is turned off, the driver can recognize that this is not caused by abnormality of the engine, but the special processing is being executed.
The engine may include a unit for stopping the engine after the unburned fuel discharge preventing unit finishes the operation. According to this feature, the engine can be naturally stopped by the inertia energy which the engine has and which is obtained from the combustion pressure after the unburned fuel is combusted.
The nature, utility, and further features of this invention will be more clearly apparent from the following detailed description with respect to preferred embodiment of the invention when read in conjunction with the accompanying drawings briefly described below.